Highly efficient diagnostic methods for monolithic sensor systems

ABSTRACT

Embodiments relate to integrated circuit (IC) sensors and more particularly to IC sensor diagnostics using multiple (e.g., redundant) communication signal paths, wherein one or more of the communication signal paths can be diverse (e.g., in hardware, software or processing, an operating principle, or in some other way) from at least one other of the multiple communication signal paths. Embodiments can relate to a variety of sensor types, implementations and applications, including 3D magnetic field and other sensors.

TECHNICAL FIELD

The invention relates generally to integrated circuit (IC) sensors andmore particularly to IC sensor diagnostics using multiple communicationsignal paths.

BACKGROUND

A recent trend in automobile drive technology, as part of developmentsin the automobile electronics sector, is for established passive safetysystems like seatbelts and airbags to be extended by active safetysystems, such as anti-lock braking systems (ABS), electronic stabilityprograms (ESP) and electrical steering systems, to provide an increasingrange of driver assistance functionalities. As has already been the casein the drive train for some time, system complexity is also continuouslyincreasing here in order to detect hazardous driving situations andcontribute to accident avoidance through active interventions by acontrol system. With ongoing technological advances, these trends areexpected to continue and grow stronger in the future.

The resulting significant increase in the number of electroniccomponents with a safety-related functionality has given rise topreviously unprecedented requirements in terms of reliability and systemavailability. In order to be able to achieve this while at the same timemeeting cost objectives, it is desired to develop efficient methods forfunctional monitoring through integrated test methods along withdesigned redundancies. At the same time, progress is desired in designmethodologies in order to be able to identify and avoid possibleweaknesses in safety systems early on. In the area of magnetic fieldsensors, for example, this has been done by the introduction of theSafety Integrity Level (SIL) standard.

In order to meet SIL standards in the automotive field, it is desired toimplement and use corresponding self-tests, including built-in tests,not only at start-up but also during normal operation, as well asautomatic monitoring structures or corresponding redundant functionalblocks and/or signal paths. Conventional magnetic sensor systems, suchHall-effect or magnetoresistive (xMR) systems, often have used asingle-channel analog main signal path, such as the one depicted as anexample in FIG. 1A in which the analog signals from a Hall sensor 10,measuring a magnetic property of a mechanical system 12, are passedthrough a single-channel path and via analog-to-digital converter (ADC)14. It is technically very difficult, or perhaps even impossible, tomeet the SIL requirements in safety-critical applications with thisconcept and therefore it is usually not possible to cover safetyrequirements with a single feed-forward sensor system.

Thus, other conventional solutions, such as the one depicted in FIG. 1B,have used two redundant magnetic field sensors 40 and 42 to meet SILrequirements. Obviously, a considerable drawback of these solutions isthe corresponding doubling of the cost, for not one but two sensors.Still other solutions, such as one depicted in FIG. 1C, propose adefined superimposed test signal 70 outside the characteristic signalfrequency ranges of the system, such as magnetic field sensors with anadditional on-chip conductor loop or pressure sensors with superimposedelectrostatic coupling to the sensor. Obviously, such test signals couldbe also generated outside the sensor system, e.g., by a device connectedto the mechanical system 72 influencing the magnetic measurement andthus providing feedback which can be diagnosed. Nevertheless, suchsetups can be more expensive, may require a higher power consumption,and may introduce influences to the main function as well and require aspecific physical set-up which is not feasible in many cases, which alsomeans they cannot be used in general.

Additionally, conventional approaches do not address or provideself-testing and related diagnostic coverage of two-dimensional (2D) orthree-dimensional (3D) sensors, which are increasingly used inautomotive and other high-integrity applications. For example, 3Dsensors can be used in angular speed applications, such as off-axisangle and angle speed measurements in brushless DC motors or steeringangle sensors, among others. The addition of a third axis can providesafety advantages using additional attributes form the relatedmechanical system, though sufficient diagnostic coverage of the sensoritself remains an important task. Fundamentally, implementing highlyintegrated and thus cost-effective diagnostic functionality for sensorswithin a given electromechanical system in safety-critical applications,such as those required to meet SIL and/or other applicable safetystandards, remains a challenge.

SUMMARY

Embodiments relate to integrated circuit (IC) sensors and moreparticularly to IC sensor diagnostics using multiple (e.g., redundant)communication signal paths, wherein one or more of the communicationsignal paths can be diverse (e.g., in hardware, software or processing,an operating principle, or in some other way) from at least one other ofthe multiple communication signal paths.

In an embodiment, a monolithic integrated circuit sensor systemcomprises a first analog-to-digital converter (ADC) in a first signalchannel; a second analog-to-digital converter (ADC) in a second signalchannel; and a first sensor device configured to sense a physicalcharacteristic, wherein the first sensor device is coupled to both thefirst and second ADCs to provide a signal related to the physicalcharacteristic to both the first and second ADCs, wherein a comparisonof signals between the first and second signal channels after the firstand second ADCs can detect an error in the sensor system.

In an embodiment, a method comprises providing a sensor systemcomprising at least one sensor to sense a first physical characteristic;providing at least two analog-to-digital converters (ADCs) coupled tothe at least one sensor; and providing circuitry to compare signals fromthe at least two ADCs to detect whether an error has occurred in thesensor system.

In an embodiment, an integrated circuit sensor system comprises a firstsensor device configured to sense a first physical characteristic andcoupled to first signal path; a second sensor device configured to sensethe first physical characteristic and coupled to a second signal path; athird sensor device configured to sense a second physical characteristicdifferent from the first physical characteristic and coupled to thesecond signal path; and circuitry coupled to the first and second signalpaths and configured to compensate at least one of a signal from thefirst sensor device or a signal from the second sensor device based on asignal of the third sensor device and to provide signals from the first,second and third sensor devices to an external control unit for a signalplausibility check using at least the signal from the third sensordevice.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1A is a block diagram of a conventional single path sensor system.

FIG. 1B is a block diagram of a conventional redundant sensor systemcomprising two sensors.

FIG. 1C is a block diagram of a conventional single path sensor systemwith a superimposed test signal.

FIG. 2A is a circuit block diagram of a sensor system according to anembodiment.

FIG. 2B is a circuit block diagram of a sensor system according to anembodiment.

FIG. 3 is an application block diagram of a system comprising two sensorsystems, wherein one incorporates a redundant measurement path accordingto an embodiment.

FIG. 4A is a diagram of a measurement signal over time according to anembodiment.

FIG. 4B is a diagram, over time, of the measurement signal of FIG. 4Aafter demultiplexing according to an embodiment.

FIG. 5A is a block diagram of an improved redundant temperaturecompensation scheme according to an embodiment.

FIG. 5B is a block diagram of a redundant compensation scheme accordingto an embodiment.

FIG. 6 is a block diagram of an angle determination and checking schemeaccording to an embodiment.

FIG. 7 is a circuit block diagram of a sensor system according to anembodiment.

FIG. 8 is a circuit block diagram of a sensor system according to anembodiment.

FIG. 9 is a circuit block diagram of a sensor system according to anembodiment.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Embodiments relate to integrated circuit (IC) sensors and moreparticularly to IC sensor diagnostics using multiple (e.g., redundant)communication signal paths, wherein one or more of the communicationsignal paths can be diverse (e.g., in hardware, software or processing,an operating principle, or in some other way) from at least one other ofthe multiple communication signal paths. Embodiments can relate to avariety of sensor types, implementations and applications, includingmultidimensional magnetic field and other sensors. In embodiments, thesensors comprise Hall-effect sensors, magnetoresistive sensors, or othermagnetic field sensors. In still other embodiments, additional or othersensors are implemented, including temperature, pressure, current,force, stray field, light, optical, mechanical stress, torque,acceleration and others. Some embodiments can use a combination ofsensors, such as one or more magnetic field sensors to sense a magneticfield and one or more related temperature sensors to provide temperaturecompensation. The sensors can be coupled to one or moreanalog-to-digital converters (ADCs), and each sensor can be coupled toan ADC in a unique or redundant signal path in embodiments. One or moreof the ADCs can comprise successive approximation ADCs (SAR-ADCs) inembodiments, though other ADCs, including flash ADCs, tracking ADCsand/or sigma-delta conversion ADCs, among others, can be used with orinstead in other embodiments.

In an embodiment, a method comprises providing a main sensor signal anda diverse method of two sensor signals measuring a physicalcharacteristic; and providing a redundant or multiplexed single signalpath, based on an analog-to-digital converter and digital signalprocessor (DSP) or analog signal path, to compensate the main sensorsignal for this physical characteristic.

Embodiments of these systems and/or methods can be configured to meet orexceed relevant safety or other industry standards, such as SILstandards. SIL standards can include automotive SILs, or ASILs. SILs canbe defined by the IEC 61508 standard, while ASILs can be defined by theISO/DIS 26262 standard as adopted from the IEC 61508 for E/E-systems forroad vehicles, at the time of filing this application, for example.These standards aim to avoid unreasonable risks of failures inincreasingly complex systems which can include software, hardware andother interrelated or interconnected components. There are fourdifferent levels (i.e., 1-4 for SIL and A-D of ASIL) which specify thelevel of risk associated with a system or component. Level 4 or D is thehighest, most stringent level, with level 1 or A being the lowest, leaststringent. This comparison does not imply that SIL 4 or ASIL D ratingscan be directly compared. For a road vehicle, an ASIL D requirementaccording to ISO 26262 could be considered to be more similar to an SIL3 requirement of the IEC 61508. This is because the scope of SIL 4rating requirements is used for large-scale industrial entities, whichcan include preventing significant environmental impacts and a highnumber of casualties, for example.

Referring to FIG. 2A, a conceptual block diagram of a sensor system 100according to an embodiment is depicted. Embodiments of system 100 can bedesigned to provide a sufficient or necessary level of diagnosticcoverage of the measurement paths of the sensors while at the same timeproviding a minimal level of redundancy to keep chip area and costrequirements to a minimum. System 100 can comprise a monolithicintegrated circuit in embodiments, or system 100 can comprise multiplechips and/or circuits in other embodiments. In still other embodiments,some functions and tasks can be carried out by externals components,including one or more receivers communicatively coupled with system 100.

System 100 comprises a three-dimensional magnetic field sensor array 110in the embodiment depicted in FIG. 2A, comprising two verticalHall-effect sensor elements 112 a and 112 b, and 114 a and 114 b, tosense each of the Bx and By components of the magnetic field,respectively, and a lateral Hall-effect sensor element 116 to sense theBz component of the magnetic field. In other embodiments, other sensortypes and/or configurations can be used. For example, system 100 cancomprise a redundant sensor configuration including a main sensor and asecondary sensor, such as Hall-effect or magneto-resistive (xMR,including GMR, AMR, TMR, etc.) sensors measuring at least one, such astwo, three or more, component of Hx, Hy, Hz and Bx, By, Bz magneticfields, though these sensors or those implemented in other embodiments,including the embodiment of FIG. 2A, can comprise other types of sensorsand are not limited to magnetic field sensors. For example, othermagnetic field, angle, current, pressure, acceleration, force, torque,optical, light or other sensors can be used in other embodiments.

System 100 can also comprise one or more additional sensors, alsoconsidered secondary, auxiliary or ancillary sensors. These sensor(s)can include temperature, force, mechanical stress, current, magneticfield or some other sensor format in various embodiments, with more thanone implemented in some embodiments (e.g., temperature and stress). Inthe embodiment of FIG. 2A, system 100 comprises a plurality oftemperature sensor elements 118 a and 118 b in a redundant configurationto measure temperatures within or proximate sensor array 110, signals ofwhich can be used for temperature compensation in embodiments. In system100, sensor elements 118 a and 118 b can be arranged proximate or formpart of (i.e., be arranged on the same die and/or in the same package)sensor array 110. In embodiments, one or more of sensor elements 118 aand 118 b are arranged proximate one or more of sensor elements 112 a,112 b, 114 a, 114 b and/or 116 in order to sense temperatures proximatethose devices. Temperatures sensed by sensor elements 118 a and 118 bthen can be used in temperature compensation calculations related tosignals from sensor elements 112 a, 112 b, 114 a, 114 b and/or 116. Asmentioned, compensation calculations also can include measurements ofadditional sensor elements, such as on-chip piezoelectric stress effectsof Hall sensors or homogenous background fields affecting a differentialmagnetic field measurement in current sensors, as only some examples.

In embodiments, a positive/negative temperature sensor scheme, i.e.,using negative temperature coefficient (NTC) sensors, can be implementedfor a redundant temperature measurement to reduce or avoid the risk ofcommon and systematic faults in the temperature measurement. In such anembodiment, the NTC values can be used in defect detection by comparingboth values with each other, while the other values (e.g., proportionalto absolute temperature, or PTAT) can be used in a signal compensationcalculation or routine. This is because the temperature measurement usesdifferent physical properties of the semiconductor (e.g., one based on abandgap voltage measurement of a semiconductor device while the other isbased on a poly-resistor value) such that it is unlikely that themeasurement results show the same faulty result if one physical propertyof the semiconductor is affected by a defect, an external influence or asystematic error. Still other sensor types, arrangements, configurationsand schemes can be implemented in other embodiments, with those depictedand discussed being only some embodiments.

Sensors other than temperature sensors can be used in embodiments,including for compensation or other purposes, as the particularconfiguration of any or all of the sensors can vary according to aparticular application. For example, sensors 118 a and 118 b cancomprise pressure sensors, stress sensors or one or more of these orother types of sensors in various embodiments. The particular exampleembodiment depicted in FIG. 2A is but one example and is not limitingwith respect to other embodiments, including any that may be embodied byor related to the claims.

In embodiments, a first biasing or reference scheme can be used forsensor elements 112 a, 112 b, 114 a, 114 b, 116 and 118 a, and a secondbiasing or reference scheme can be used for sensor elements 118 b. Inother words, the main signal (e.g., the magnetic field sensed by thesensor comprising sensor elements 112 a, 112 b, 114 a, 114 b and 116)and a first temperature measurement from sensor elements 118 a can havethe same biasing in one embodiment, while the second temperaturemeasurement from sensor elements 118 b has a different biasing.Variations of biasing and/or reference schemes can be used in otherembodiments.

Sensor array 110 (which refers generally herein to sensor elements 112a, 112 b, 114 a, 114 b, 116, 118 a and 118 b unless otherwise mentionedor explained) is communicatively coupled to a first multiplexer (MUX)120 a and a second MUX 120 b. In one embodiment depicted in FIG. 2A,sensor elements 112 a, 112 b and 118 a are coupled with MUX 120 a;sensor elements 114 a, 114 b and 118 b are coupled with MUX 120 b; andsensor element 116 is coupled with both MUX 120 a and 120 b. Thiscoupling arrangement in the context of MUX 120 a and 120 b (and ADC 122a and 122 b) will be discussed in more detail below.

Each MUX 120 a and 120 b is communicatively coupled with an ADC 122 aand 122 b, respectively. Any ADC, such as a flash, tracking, single- ordual-slope, successive-approximation register (SAR),successive-approximation tracking (SAT), Nyquist-rate, noise-shapingsigma-delta, averaging dual slope or another ADC can be used. While ADCs122 a and 122 b can be the same type of ADC in embodiments, they neednot be so in other embodiments for diversity considerations, e.g., toavoid systematic faults that could result from using a single design.

As previously mentioned, sensor elements 112 a, 112 b and 118 a arecoupled with MUX 120 a; sensor elements 114 a, 114 b and 118 b arecoupled with MUX 120 b; and sensor element 116 is coupled with both MUX120 a and 120 b in the embodiment of FIG. 2A. There are at least severaladvantages to such a configuration. First, the X and Y signals (i.e.,the Bx and By magnetic field components) sensed by sensor elements 112a/112 b and 114 a/114 b can be sampled synchronously, as sensor elements112 a and 112 b are coupled with MUX 120 a while sensor elements 114 aand 114 b are coupled with MUX 120 b. Second, the Z signal (i.e., the Bzmagnetic field component) can be sampled redundantly and via twodifferent signal channels, as sensor element 116 is coupled with bothMUX 120 a and MUX 120 b. Third, two temperature measurements can beobtained (i.e., a first via sensor elements 118 a coupled to MUX 120 a,and a second via sensor elements 118 b coupled to MUX 120 b).

FIGS. 4A and 4B assist in illustrating some of these advantages, alongwith basic operation and one example of a multiplexing scheme of valuesfrom sensor array 110, MUCs 120 a and 120 b, ADCs 122 a and 122 b,demultiplexers (DEMUXs) 124 a, 124 b and other circuitry of system 100in an embodiment. FIG. 4A illustrates output signal sequences from ADCs122 a and 122 b at (A) in FIG. 2A. ADC 122 a outputs a recurringsequence of X (sensor elements 112 a and 112 b, T (sensor elements 118a), X and Z (sensor element 116). ADC 122 b outputs a recurring sequenceof Y (sensor elements 114 a and 114 b), Z (sensor element 116), Y and T(sensor elements 118 b). In an embodiment, the X and Y measurements aresynchronous, as illustrated in FIG. 4A, which can be advantageous for aprecise angle calculation. The redundant Z measurements enable a checkof ADC 122 a vs. ADC 122 b to detect an error that may occur in one orthe other (or, if the same at each, in ADCs 122 a, 122 b in someembodiments). For example, a value change between successive Zmeasurements of redundant ADCs can be used to detect defects if thedifferent in values is within or out of an acceptable predeterminedrange. In some embodiments, the third axis (e.g., Z) measurement can beused solely for a plausibility or operability check of ADCs 122 a and122 b, as the same sensor signal is processed sequentially by redundantADCs 122 a and 122 b. This can be advantageous when usingmagneto-resistive sensors for the X/Y axis measurement (i.e., directionof Hx/Hy fields) and a Hall sensor element for the Z axis measurement(i.e., magnetic flux density or Bz), which includes in addition tochecking the ADCs 122 a, 122 b an additional operability check of thesystem 100 together with the external mechanical system (e.g., mountingof the sensor or an external magnet). The temperature measurements viasensor elements 118 a and 118 b are redundant and independent, as shown,and in embodiments can enable detection of biasing defects, as in atleast one embodiment sensor elements 118 a and 118 b are differentlybiased as discussed above. This further provides an operability check ofsensor array 110. In embodiments, the sampling rates of ADCs 122 a and122 b are at least twice the required overall sample rate of sensorsystem 100 in order to allow for multiplexing of two channels.

The signals output by ADCs 122 a and 122 b (e.g., those depicted in FIG.4A) are then communicated to two demultiplexers (DEMUX) 124 a and 124 b.The signals after DEMUXes 124 a and 124 b, at (B) in FIG. 2A, aredepicted in FIG. 4B. The lowercase signal designators indicate that thevalue is the same as the last, which is stored follows from themeasurement sequence as repetition. In other words, X and Y are sampledsynchronously, then Z and the first T are sampled, then X and Y again,then Z again and the second T, etc. Flipping the two measurements of Zand T and changing the source and method for T allows the detection timeor period of a variety of defects or errors, including a bad temperaturemeasurement (i.e., due to the two sources for T), an error in ADC 122 aor 122 b (i.e., due to providing a Z value from the same sensor elementto different ADCs), an error in temperature compensation (i.e., due tousing different methods for T measurement and using separate DEMUXs andADCs) or a digital signal processor (DSP) (i.e., due to using differentcompensation methods for the two methods of T measurements and similar Zvalues), an error in DEMUX 124 a or 124 b (i.e., communicating similarand different values through these elements) and/or others. This shortdetection time provides advantages for quick detection (e.g., within afew measurement samples) of errors, defects or other problems in system100 without the drawbacks discussed above with reference to FIGS. 1A, 1Band 1C.

Returning to FIG. 2A, after (B) the signals from the main sensorelements (e.g., the X, Y and Z signals) can be compensated. Aspreviously discussed, temperature compensation is used for the magneticfield sensor elements of system 100, but other compensation types andmethodologies can be used in other embodiments, with magnetic fieldsensor elements or some other type of sensor element. In system 100,this temperature compensation takes place at 126 x, 126 y and 126 z,with the demultiplexed temperature signal (FIG. 4B) from DEMUX 124 bprovided to each compensation block 126 x, 126 y and 126 z. In oneembodiment, the same temperature compensation routine can be implementedby each compensation block 126 x, 126 y and 126 z, though in otherembodiments different routines can be used.

In another embodiment, a value scheme can be implemented in accordancewith FIG. 4B in which time-multiplexed and value-multiplexed samples ofmain and secondary channels are transmitted to an external ECU or otherdevice. In the ECU or other device, either the time-multiplexed, thevalue-multiplexed or both samples can be used in a comparison orverification of data from one or more of the sensors, channels or othersystem components. For example, it has been discussed how temperature orother secondary sensor data can be used to compensate data or signals ofa main sensor, such as a magnetic field sensor. In embodiments, thecompensation data or information from the temperature or other secondarysensor data can in addition or instead be used in a plausibility checkby the ECU to confirm that the data or information is as expected. Inone embodiment, data from multiple secondary sensors can be compared inthe ECU to confirm that it is the same, within some range, or conformsto some other predefined characteristic. In another embodiment, anoverall compensation signal can be checked with respect to an acceptedor expected range or value. For example, if a system has an expectedoperating temperature range of 30 degrees C. to 70 degrees C. and atemperature sensor provides a reading of 90 degrees, it may be morelikely that the temperature sensor has malfunctioned (or that at errorhas occurred somewhere within the system) than that the system isoperating at a temperature that much higher than the expected range. Inanother example, one temperature sensor measuring 50 degrees and anothermeasuring 80 degrees could indicate a sensor and/or system error.Transmitting this data to the ECU or other device and using it for aplausibility check or other comparison it can provide an additional oralternative level of diagnostic coverage.

FIG. 2B shows another embodiment that, in contrast to FIG. 2A, comprisesa one-dimensional sensor 140 a. As previously discussed, the type ofsensor(s) implemented in any embodiment can vary (e.g., FIG. 2B depictsa one-dimensional Hall sensor but can comprise some other type of sensorin other embodiments), and principles of the embodiments of FIG. 2A or2B can apply to the other, or to other embodiments and examplesdiscussed herein. Like the system of FIG. 2A, the system of FIG. 2B alsoimplements features and aspects of resource sharing. For example, afirst signal path comprising the first or main sensor 140 a and a firstADC 141 a can be a primary or dedicated measurement path for the mainsignal, while a secondary signal path incorporates a redundant secondsensor 140 b (e.g., another one-dimensional Hall sensor, or some othertype of sensor) and a second ADC 141 b. ADC 141 b can be embedded in orwith a signal multiplexer (MUX) 142 and demultiplexer 143. While adiagnosis of the main signal measured by sensor 140 a can be compared bya second signal from sensor 140 b, a temperature or other compensationmeasurement can be conducted using a diverse setup of a positivetemperature coefficient sensor 147 a and a negative temperaturecoefficient sensor 147 b, signals from both of which can be converted byADC 141 b. Additional measurements, such as measuring on-chip stress orsome other physical quantity by a sensor 148, also can be provided toADC 141 b.

In principle, ADC 141 b can be an independent ADC for sensor 140 b inembodiments, if advantageous or suitable for, e.g., performance or otherreasons. The embodiment of FIG. 2B, however, is an example of a highlyefficient implementation that does not sacrifice functional diagnosis ofthe sensor system. Following the ADCs 141 a and 141 b, the signals canbe processed by processing circuitry 145, similar to other embodiments,and communicated to an ECU or other device via interface 146. Inembodiments, the signals from each signal path are provided to the ECUindependently, such as in two separate data streams. The signals can beprotected using a cyclic redundancy check (CRC) 149 a, 149 b for eachpath. In the embodiment of FIG. 2B, the signal processing circuitry canalso include a redundant re-calculation of the first signal processingresult, though this can omitted in some embodiments.

As previously mentioned, some embodiments can implement positive andnegative temperature compensation schemes. FIG. 5A is a block diagram ofone such scheme, in which raw data is input, two different compensationschemes are implemented (one positive, PTC-based compensation, and onenegative, NTC-based compensation), and compensated data is output. Tptcand Tntc calculations can introduce alterations to the calculations, andthe results can be compared to detect errors, such as within apredefined tolerance. Such a scheme enables detection of systemic faultsas well as intermittent or random faults that can occur in thecompensation algorithm or related hardware, including a DSP or hardwarepath. In one embodiment comprising a diverse implementation, a bandgapprinciple can be implemented for the positive temperature compensationand a poly-resistor for the negative temperature compensation. Usingdifferent calculation schemes, two values can be determined and providedfor evaluation to detect the aforementioned and other errors or defects.

FIG. 5B shows a more generalized approach, in which a physical behavioris measured using redundant sensors that use certain compensation bysub-sensors. By using inverse mechanisms for the sub-sensors, e.g., aPTC and NTC behavior (if the compensation is temperature dependent;similar approaches can be implemented for stress or other dependencies),a redundant setup with diverse compensation principles can significantlyincrease the tolerance with respect to systematic faults of theimplementation. As the compensation schemes are inherently different, itis also possible to jointly implement them in one signal processingblock, assuming that a certain fault model will have a different effecton the two schemes, causing a detectable deviation between the channels.If the focus for fault tolerance resides on the signal processing, thepaths can be implemented redundantly while the main sensors (in1 andin2) can be joined to a single sensor in supplying both signalprocessing paths with its sensor data.

FIG. 3 depicts an application of such a redundant sensor system 150together with a second non-redundant sensor system 152 (which can beanother redundant sensor system as well), where the results of thedifferent paths can be used to replace each other for the main algorithmor the check algorithm in ECU 154 implementing the system functionalityof the electrical and/or electronic (E/E) system. This setup allowscontinuing of operation if one of the sensors main1, main2, sub or itsrelated bias domain or following signal path fails; only if two of thethree sensors fail, system 150 can be set to a safe state or cancontinue in a degraded or reduced operation mode, which is dependent onthe level of safety required. In another embodiment, a second redundantsensor similar to 150 used for the second sensor system 152 can prolongoperation when two sensors fail or if one of the two sensor systemsfails completely.

Furthermore, in a 3D sensor the main calculation can comprise two sensorsignals X and Y that are temperature compensated in a first processingpath 160 while the sub sensor uses the sensor signal Z, which is alsomultiplexed with the two processing paths 160, 162 similar to the schemeshown in FIGS. 4A and 4B.

Returning to FIG. 2A while also referring to FIG. 6, an angledetermination can be made at ARCTAN block 128 from thetemperature-compensated X and Y measurements, such as by determining thearctangent of an angle between the X and Y component measurements. Thisangle determination also is shown in the first portion of FIG. 6.Following the angle determination, a plausibility check can beimplemented using additional sine and cosine functions and comparing oneor both of these with the X and/or Y values. In one embodiment, both thesine and cosine are used for an increased level of fault or errordetection, though in other embodiments it can be sufficient to determineonly one or the other. Additionally, the plausibility check can becarried out on-chip or off-chip in embodiments.

The angle calculation at ARCTAN block 128 can be carried out on-chip,and the calculation can be verified in one embodiment by a recalculationoff-chip after the compensated X, Y and Z values as well as thecalculated angle α are transmitted to a receiver or other device orcircuitry via interface 130. Additional checks also can be performedwithin, by or for system 100. For example, comparators 132 z and 132 tcan be used to check for expected values of Z and T, such as within somepredefined tolerance(s). Temperature limits can also be checked bytemperature limit block 134. WARN signals or flags can be provided tointerface 130 by comparators 132 z or 132 t, or block 134, or in otherembodiments any WARN signal can trigger some behavior or action byinterface 130 for communication or detection off-chip, such as using analternate pulse-width modulated (PWM) frequency, clamping, or switchinginterface 130 off, as examples. The compensated X, Y and Z signals at(C) optionally can be clocked, such as to introduce a delay in order tosynchronize one or more of the signals and/or calculations. In relationto the application shown in FIG. 3, an alternate, redundant sensorsystem can be implemented for 150, where the first sensor systemdelivers X/Y vectors from an angular measurement plus the correspondingangle and length of the resulting vector, and the second sensor systemdelivers the X/Y vectors only. ECU 154 uses this redundancy in a similarmethod for a failover scenario when either the first X/Y or the secondX/Y vectors do not match with the delivered angle signal, e.g., causedby a defective sensor or sensor path. One implementation uses a high-endGMR angular sensor comprising digital compensation and output of X,Y andangle information including the diagnostic methods mentioned, and asecond GMR sensor bridge comprising only an X and Y vector that isconverted and used in ECU 154. In this sense, multiple variations ofsensors and processing methods for such an application are possible.

Coming back to the sensor system as shown by 100 and used in application122, further adaptations can be made, or other implementations used, toaccommodate particular characteristics of an application, sensor type orother factor. For example, while sensor system 100 comprised a 3D sensor110, a similar (though perhaps simplified) system 200 can be implementedfor a 1D sensor, as depicted in FIG. 7.

System 200 comprises redundant signal paths or channels and redundantsensors 202 a and 202 b configured to sense the target characteristicand therefore can be considered to be the primary measurement sensors inthis system. For example, and continuation the example of system 100 ofFIG. 2A, sensors 202 a and 202 b can comprise magnetic field sensors,though in contrast with sensor 110 of system 100 are 1D sensors. Sensor202 b can be used to perform a plausibility check of sensor 202 a andthus can be the same as or merely similar to sensor 202 a. For example,both sensors 202 a and 202 b can comprise magnetic field sensors, thoughsensor 202 b can be a less expensive, less complex sensor, as the higheraccuracy desired of sensor 202 a is not necessary in some embodiments.

System 200 also comprises secondary sensors 204 a and 204 b, which canbe similar to temperature sensor elements 118 a/b of system 100.Secondary sensors 204 a and 204 b can be implemented for compensation,trimming or some other secondary purpose and can comprise temperature,pressure, or some other suitable type of sensor, as discussed above withrespect to system 100. For example, sensors 204 a and 204 b can comprisetemperature sensors used for temperature compensation, with one ofsensors 204 a or 204 b implementing a first compensation scheme (e.g.,positive temperature compensation using, e.g., PTAT) and the other ofthe sensors 204 b or 204 a implementing a second compensation scheme(e.g., negative temperature compensation).

Sensors 202 a and 204 b are coupled to a first MUX 206 a, and sensors202 b and 204 a are coupled to a second MUX 206 b. MUX 206 a is coupledto a first ADC 208 a, and MUX 206 b is coupled to a second MUX 208 b.ADCs 208 a and 208 b can comprise virtually any type of ADC, includingthose discussed above with respect to system 100. ADCs 208 a and 208 bare coupled to a DSP 210, which is in turn coupled to an interface 212,which can be a single or dual interface in embodiments. In otherembodiments, system 200 can comprise more than one DSP, such as a firstDSP coupled to the ADC 208 a and a second DSP coupled to ADC 208 b.

In operation, a first bias signal is applied to sensors 202 a and 204 aby bias 214 a, and a second bias signal is applied to sensors 202 b and204 b by bias 214 b. Measurement signals are communicated by sensors 202a, 202 b, 204 a and 204 b to ADCs 208 a and 208 b via MUXs 206 a and 206b as depicted. The signal at ADC 208 a is D1, DB, D1, DB . . . , whereD1 is data from sensor 202 a and DB is data from sensor 204 b. Thesignal at ADC 208 b is DA, D2, DA, D2 . . . , wherein DA is data fromsensor 204 a and D2 is data from sensor 202 b. These signals areprovided to DSP 210, which can implement first and second trimming orcompensation algorithms in embodiments. For example, a first algorithmcan be a direct polynomial, and a second an inverse polynomial, thoughothers can be used in other embodiments. Output signals of DSP 210 areprovided to interface 212, for example D1 with DA, D2 with DB, D1 withDA, D2 with DB . . . , wherein D1 with DA should be the same as D2 withDB. If they are not equal, an error has occurred and by this comparisoncan be detected.

In embodiments, the upper signal path or channel (e.g., that comprisingsensor 202 a, with “upper” referring only to the layout of FIG. 7 on thepage) is a higher accuracy channel, while the channel of sensor 202 b isa less accurate channel, relative to the channel of 202 a. Such aconfiguration can help to reduce costs while still providing redundancyand fault detection. The different compensation schemes implemented bysensors 204 a and 204 b also can have different accuracies, with thescheme implemented by sensor 204 b being of lower accuracy as part ofthe lower accuracy channel, at least in this example. Additionally, thechannels can be sampled at different rates, with the higher accuracychannel generally sampled at a higher rather than the less accuratechannel. For example, the less accurate channel can be sampled every nthvalue in one embodiment. Finally, the less accurate channel can use adifferent conversion method in one embodiment, which is furtheroptimized either for robustness, cost of implementation, or both.

Still another example embodiment of a system 300 is depicted in FIG. 8,with system 300 comprising a basic setup still sufficient to providebasic diagnostic coverage. For example, in on embodiment system 300provides diagnostic coverage in that it can provide a warning or alertif at error occurs, though system 300 may not be able to localize theerror (i.e., identify which component, circuitry or measurement causedthe error).

In FIG. 8, system 300 comprises at least one primary sensor 302, such asone like sensor 110 of FIG. 2A or any of the other sensors discussedherein or suitable for applications of one or more of the systems.System 300 also comprises at least two secondary sensors 304 and 306,which can comprise, e.g., temperature sensors in one embodiment, or someother type(s) of sensors in other embodiments. Sensors 304 and 306 canbe configured to have or implement different characteristics as part ofthe diagnostic coverage provided by system 300. In one embodiment,sensor 304 can sense direct behavior, while sensor 306 can sense theinverse behavior of sensor 304 (e.g., positive and negative, similar toother embodiments discussed herein). Still other embodiments can useother, different behaviors or operations of sensors 304 and 306.

System 300 also comprises basic circuitries 308 a and 308 b coupled tosensors 302 and 304, and sensor 306, respectively. Circuitries 308 a and308 b can provide biasing, as discussed elsewhere herein, and otherbasic functionalities and infrastructure for operation, as appreciatedby those skilled in the art.

The primary channel or path of sensor 302 also comprises MUX 310 a andADC 308 a, wherein these components can be similar to or different fromthose of similar components discussed elsewhere herein with respect toother embodiments. For example, ADC 308 a (as well as ADC 308 b) cancomprise a SAR-ADC, a tracking ADC, a flash ADC, a sigma-delta ADC, orsome other ADC in various embodiments. The signal path of sensor 306comprises MUX 310 b and ADC 308 b, and both ADCs 308 a and 308 b arecoupled to DSP 310. In other embodiments, as previously mentioned, morethan one DSP can be included in system 300. DSP 310 is coupled tointerface 312, with first and second trimming algorithms similar to asdiscussed above with respect to system 200 in at least one embodiment.In other embodiments, another interface can be included in system 300,such as one that is multiplexed (e.g., physically or time-multiplexed)to accommodate the dual-channel configuration of system 300.

Advantages of system 300 include a potentially simplified, lower costimplementation of a system which provides diagnostic coverage that issufficient to meet at least minimum standards. Such an implementationcan be advantageous in some applications and configurations.

Yet another system 400 is depicted in FIG. 9. System 400 is similar toboth systems 200 and 300, and similar reference numerals (e.g., 202 aand 402 a; 308 a and 408 a, etc.) are used herein throughout to refer tosimilar elements unless otherwise discussed or made clear from thediscussion. System 400 can comprise at least one up to an arbitrarynumber of sensors. Like system 200, system 400 comprises a primarysensor 402 a in a first channel and a secondary sensor 402 b in a secondchannel, where primary and secondary sensors 402 a and 402 b can be thesame type of sensors (e.g., magnetic field, current, etc.) inembodiments. Additional ones of these sensors 402 a and 402 b also canbe included in system 400, as illustrated. Additional sensors 404 a and404 b are included in each channel and can comprise temperature,pressure or other suitable types of sensors that can be used tocompensate or trim sensors 402 a and 402 b. In embodiments, and as insystem 300 and others discussed herein, sensors 404 a and 404 b canimplement different behaviors to provide diversity and/or plausibilitychecks of system 400. For example, they can be the inverse of oneanother, one can be positive and the other negative (e.g., PTC and NTC),etc. In embodiments, separate physical sensors are used for, e.g., theinverse, to reduce the risk of common-cause failures if a single sensorwith merely its measurement signal inverted was used, though this couldbe implemented in some embodiments if the application or use weresuitable and could allow for it.

The remaining components and operation of system 400 can be quitesimilar to those of other systems discussed herein (e.g., systems 200and 300). System 400 is generally more symmetric between the first andsecond channels than system 300, in embodiments, and can exceed theminimum configuration of that system. Those skilled in the art willappreciate that other modifications and adaptations can be made to theparticular systems depicted herein, such as to adapt to or accommodate aparticular application or use or for some other purpose. The systemsdepicted and discussed herein therefore are merely examples used toillustrate various possibilities falling within the scope of the claims.

Numerous advantages can be provided by embodiments. For example, thereuse of some system components and/or routines can reduce chip area anddevelopment efforts while still providing a high level of integritychecking that meet or exceed applicable standards. Additionally,components related to the main or target signal can be arrangedtogether, with only some add-on components for, e.g., compensation bytemperature sensing with independent biasing, needed.

Another advantage is the high-level and number of faults and errors thatcan be detected in embodiments. These include those related to sensorbiasing, ADCs, input multiplexing, supply voltage and current, outputdemultiplexing, DSP, angle calculation, compensation, interfacing, datastorage, and still others. These are others can be accomplished, inpart, by arrangements and methodologies discussed herein, includingimplementing independent temperature measurement, multiplexing at leastone sensor axis measurement, plausibility checks and signal comparisonsat various points, calculations carried out both on- and off-chip, usingdifferent vector lengths, using different parameter sets, polynomials,and/or different formulas, inversions and positive/negativeconfigurations, among others.

Various embodiments of systems, devices and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the invention. It should be appreciated,moreover, that the various features of the embodiments that have beendescribed may be combined in various ways to produce numerous additionalembodiments. Moreover, while various materials, dimensions, shapes,configurations and locations, etc. have been described for use withdisclosed embodiments, others besides those disclosed may be utilizedwithout exceeding the scope of the invention.

Persons of ordinary skill in the relevant arts will recognize that theinvention may comprise fewer features than illustrated in any individualembodiment described above. The embodiments described herein are notmeant to be an exhaustive presentation of the ways in which the variousfeatures of the invention may be combined. Accordingly, the embodimentsare not mutually exclusive combinations of features; rather, theinvention can comprise a combination of different individual featuresselected from different individual embodiments, as understood by personsof ordinary skill in the art. Moreover, elements described with respectto one embodiment can be implemented in other embodiments even when notdescribed in such embodiments unless otherwise noted. Although adependent claim may refer in the claims to a specific combination withone or more other claims, other embodiments can also include acombination of the dependent claim with the subject matter of each otherdependent claim or a combination of one or more features with otherdependent or independent claims. Such combinations are proposed hereinunless it is stated that a specific combination is not intended.Furthermore, it is intended also to include features of a claim in anyother independent claim even if this claim is not directly madedependent to the independent claim.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

What is claimed is:
 1. A monolithic integrated circuit sensor systemcomprising: a first analog-to-digital converter (ADC) in a first signalchannel; a second analog-to-digital converter (ADC) in a second signalchannel; and a first sensor device configured to sense a physicalcharacteristic, wherein the first sensor device is coupled to both thefirst and second ADCs to provide a signal related to the physicalcharacteristic to both the first and second ADCs, wherein a comparisonof signals between the first and second signal channels after the firstand second ADCs can detect an error in the sensor system.
 2. The sensorsystem of claim 1, wherein the first sensor device is coupled to thefirst ADC by a first multiplexer in the first signal channel, andwherein the first sensor device is coupled to the second ADC by a secondmultiplexer in the second signal channel.
 3. The sensor system of claim1, wherein the first sensor device is configured to provide a pluralityof signals related to the physical characteristic, wherein a first ofthe plurality of signals is provided to the first ADC, a second of theplurality of signals is provided to the second ADC, and a third of theplurality is the signal related to the physical characteristic providedto both the first and second ADCs.
 4. The sensor system of claim 3,wherein the first sensor comprises a magnetic field sensor, and whereinthe first of the plurality of signals relates to a first component of amagnetic field, the second of the plurality of signals relates to asecond component of the magnetic field, and the third of the pluralityof signals relates to a third component of the magnetic field.
 5. Thesensor system of claim 4, wherein the sensor system is configured todetermine an angle of the magnetic field from the first and second ofthe plurality of signals.
 6. The sensor system of claim 1, wherein thesensor system is coupled to a receiver, and wherein the receiver isconfigured to recalculate the angle of the magnetic field.
 7. The sensorsystem of claim 1, further comprising at least one second sensor deviceconfigured to sense a characteristic related to the first sensor device.8. The sensor system of claim 7, wherein a first second sensor device iscoupled to the first signal channel and a second sensor device iscoupled to the second signal channel, and wherein a comparison ofsignals related to the first and second sensor devices between the firstand second signal channels after the first and second ADCs can detect anerror in the sensor system.
 9. The sensor system of claim 8, wherein theat least one second sensor device comprises at least one of atemperature sensor, an optical sensor, a light sensor, a stray fieldsensor, or a mechanical stress sensor.
 10. The sensor system of claim 8,wherein the first second sensor device is configured to implement afirst type of measurement scheme and the second sensor device isconfigured to implement a second type of measurement scheme.
 11. Thesensor system of claim 10, wherein the first and second types ofmeasurement schemes are the inverse of one another.
 12. The sensorsystem of claim 11, wherein the first type of measurement scheme is acompensation scheme using a positive scheme or a direct scheme, and thesecond type of measurement scheme is a compensation scheme using anegative scheme or an inverse scheme.
 14. The sensor system of claim 8,wherein a first biasing is applied to the first second sensor device anda second biasing is applied to the second sensor device.
 15. The sensorsystem of claim 7, wherein a signal from the at least one second sensordevice is used to compensate a signal related to the first sensordevice.
 16. The sensor system of claim 15, further comprising a digitalsignal processor (DSP) coupled to the first and second signal channels,wherein the DSP is configured to implement a first compensationalgorithm for a signal received from the first ADC and a secondcompensation algorithm for a signal received from the second ADC,wherein the first compensation algorithm and the second compensationalgorithm are different, and wherein a comparison of signals after thefirst and second compensation algorithms can indicate an error hasoccurred in the sensor system.
 17. A method comprising: providing asensor system comprising at least one sensor to sense a first physicalcharacteristic; providing at least two analog-to-digital converters(ADCs) coupled to the at least one sensor; and providing circuitry tocompare signals from the at least two ADCs to detect whether an errorhas occurred in the sensor system.
 18. The method of claim 17, whereinproviding a sensor system further comprises providing at least onemulti-dimensional sensor coupled to the at least two ADCs to provide asignal related to one dimension to both of the at least two ADCs. 19.The method of claim 17, wherein providing a sensor system furthercomprises providing at least one additional sensor to sense a secondphysical characteristic related to an environmental characteristic. 20.The method of claim 19, further comprising providing circuitry to do atleast one of: compensate signals of the at least one sensor to sense thefirst physical characteristic by signals of the at least one additionalsensor to sense the second physical characteristic; compare signalsrelated to the at least one additional sensor to sense the secondphysical characteristic to detect whether an error has occurred in thesensor system; providing a second sensor to redundantly sense the firstphysical characteristic; and providing at least two additional sensorsto sense the second physical characteristic related to an environmentalcharacteristic, and comparing signals of the at least two additionalsensors to detect an error in the sensor system.
 21. The method of claim20, wherein the sensor system comprises at least two independent sensorpaths related to the first physical characteristic, wherein providingcircuitry further comprises providing circuitry to compensate signals ofa first independent sensor path using a first compensation scheme, andproviding circuitry to compensate signals of a second independent sensorpath using a second compensation scheme that is different from the firstcompensation scheme.
 22. The method of claim 21, wherein the sensorsystem comprises at least two sensor paths related to the first physicalcharacteristic, wherein at least a portion of the at least two sensorpaths overlaps, and wherein providing circuitry further comprisesproviding circuitry to compensate signals of a first independent sensorpath using a first compensation scheme, and providing circuitry tocompensate signals of a second independent sensor path using a secondcompensation scheme that is different from the first compensationscheme.
 23. An integrated circuit sensor system comprising: a firstsensor device configured to sense a first physical characteristic andcoupled to first signal channel; a second sensor device configured tosense the first physical characteristic and coupled to a second signalchannel; a third sensor device configured to sense a second physicalcharacteristic different from the first physical characteristic andcoupled to the second signal channel; and circuitry coupled to the firstand second signal channels and configured to compensate at least one ofa signal from the first sensor device or a signal from the second sensordevice based on a signal of the third sensor device and to providesignals from the first, second and third sensor devices to an externalcontrol unit for a signal plausibility check using at least the signalfrom the third sensor device.